In cataract surgery, there has been widely performed removal of opacified crystalline lenses by phacoemulsification and aspiration (PEA) followed by implantation of intraocular lenses into aphakic eyes. There are two types of intraocular lens: a hard intraocular lens whose optic is made of a hard material such as PMMA and a soft intraocular lens whose optic is made of a flexible material such as silicone elastomer, soft acrylic or hydrogel.
Upon use of a hard intraocular lens, the lens needs to be inserted through an incision having been cut in a cornea or sclera in a width approximately the same as the diameter of the optic of the lens. On the other hand, upon use of a soft intraocular lens, the lens can be inserted through an incision smaller than the diameter of the optic of the lens by folding the optic.
In order to reduce the risk of post-surgery corneal astigmatism or infection, insertion of a lens through a small incision is preferable. Consequently, soft intraocular lenses tend to be preferred now. There are three types of soft intraocular lens: Type 50 whose optic is made of a soft material and supporting portions are made of a hard material such as PMMA (generally, this type of intraocular lens has two thin filament-shaped supporting portions (FIG. 9A); Type 51 whose optic and supporting portions are made of the same soft material (generally, this type of intraocular lens has plate-like supporting portions (FIG. 9B); and Type 52 which has two or more thin plate-like supporting portions (FIG. 9C).
In addition, a dedicated intraocular lens insertion device having a mechanism to lead an intraocular lens to an eye through a slender tube is used in some cases in order to insert intraocular lenses into eyes. By using such an intraocular lens insertion device, an intraocular lens can be inserted through an incision opening smaller than 3 mm.
In recent years, in order to eliminate the possibility of bacterial contamination or operational error in handling intraocular lenses, an intraocular lens insertion device where an intraocular lens is set beforehand and which can be packaged and stored has been developed.
With such an intraocular lens insertion device, however, there was a problem that a supporting portion arranged in the backward direction of a lens advancing axis (hereinafter, referred to as a trailing supporting portion) got caught in the gap between a plunger for pushing out the intraocular lens and an inner wall of a passage of the insertion device or entangled in the plunger in a process of movement of the intraocular lens. Such a problem is brought to the fore especially with a soft intraocular lens having thin filament-shaped supporting portions or a soft intraocular lens having thin plate-like supporting portions.
In such an intraocular lens insertion device, if the trailing supporting portion stretches in a process of movement of the intraocular lens, the trailing supporting portion is left outside of the eye when the lens is inserted through a small incision in the eye. Therefore, after the lens is pushed by the plunger, a repeated operation for inserting the trailing supporting portion into the eye is required, and it takes time and labor in surgery. In some cases, while the intraocular lens is moving inside the intraocular lens insertion device, the optic and the trailing supporting portion interfere with each other, resulting in damage or breakage of the optic or the trailing supporting portion.
Therefore, when an intraocular lens is inserted into an eye using the intraocular lens insertion device, the behavior of the trailing supporting portion of intraocular lens needs to be controlled appropriately in a process of movement of the intraocular lens.
In view of the foregoing problems, a lens insertion tool which has a side clearance provided at the distal end of a plunger for accommodating a trailing supporting portion to prevent damage to the trailing supporting portion has been disclosed (Patent Document 1, for example). A lens insertion tool provided with a relief channel for a trailing supporting portion at the lower side of a plunger has been also disclosed (Patent Document 2, for example). Furthermore, a lens insertion tool wherein a plunger pushes a trailing supporting portion up a ramp and bends haptics up and over IOL has been disclosed (Patent Document 3, for example). Thus, the above-mentioned Patent Documents can reduce getting caught of a trailing supporting portion of intraocular lens having thin filament-shaped or plate-like supporting portions.
Patent Document 1: Japanese Translation of PCT International Application No. 11-506357
Patent Document 2: U.S. Pat. No. 6,733,507
Patent Document 3: Japanese Unexamined Patent Publication No. 2004-351196